It is well known that the traction of vehicles on soft terrain such as sand, mud and snow may be greatly improved by decreasing the pressure within the pneumatic tires on which the vehicles ride. By decreasing the pressure, the tire supporting surface will increase, thereby enlarging the contact area between the tires and the terrain.
Additionally, it is often desirable to decrease tire pressure to increase riding comfort on rough roads and to accommodate low strength road systems as well as off-road surface variances. For example, low tire inflation pressure enhances the mobility of military amphibious vehicles as well as high-speed, high mobility military vehicles. Operation at such relatively low tire inflation pressures improves off-highway vehicle performance, durability, reliability and reduced life cycle operating costs. Consideration of these costs not only includes the condition of the driver, vehicle and cargo but also the roads over which the vehicles travel.
One problem in operating pneumatic tires at such low operating pressures is that the beads of the pneumatic tire tend to separate from the wheel rim. One solution to this problem is to provide bead locks which lock the tire beads to the wheel rim to retain a minimal air pressure in the tire cavity so that the vehicle can operate in such difficult terrain. Some bead locks also function as a limited run-flat mechanism.
One such tire support system or bead lock is described in U.S. Pat. No. 4,383,566. The bead lock includes material which expands due to heat caused by a flat condition to support the tire in normal configuration until repairs can be effected. The bead lock provides initial support to prevent sidewall damage due to flexing and prevents the beads from falling into the wheel well by swelling to fill the cavity. There is no contact in normal tire operation with either sidewall or inner tread surface.
The U.S. Pat. No. 632,028 to Smith discloses an annular fastening band which seats in the central groove of a wheel rim and serves to bind or clench the casing of the tire into abutment with the wheel rim. The fastening band uses strengthening rods which join at diametrically opposed locking ends.
The U.S. Pat. Nos. 1,652,146 and 1,653,147 to Michelin disclose the use of arcuate plates in conjunction with a wheel rim to secure the bead lock.
The U.S. Pat. No. 4,078,597 to Noda discloses an inflatable tubular ring disposed in the central well of the wheel to secure the bead lock.
The U.S. Pat. No. 4,122,882 to Fisher et al discloses an obstructor band which includes upstruck lugs to maintain the tire bead in abutting relation with the wheel rim.
A first U.S. Pat. No. 4,304,282 to Watts discloses a blocking member which is mounted for movement between first and second positions within the wheel drop center.
A second U.S. Pat. No. 4,374,535 to Watts discloses a wheel well filler which seats or mounts in the well of the wheel to prevent removal of the tire beads over the side flanges during operation of the tire in a deflated condition. The filler is molded from a flat, resilient, flexible material. The filler is reinforced by a steel wire cable molded integrally with the filler. A hook and eye latch locks the filler in position in the wheel well.
The U.S. Pat. No. 4,391,317 to Savage discloses a band which has box section legs spaced on its interior surface. The band device mounts in the drop center of the wheel.